From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Report comparing Firth's Crown Austenitic steel and Silchrome for exhaust valves, and commenting on an Armstrong Siddeley gearbox.
Identifier | ExFiles\Box 19\5\ Scan056 | |
Date | 11th April 1930 guessed | |
-6- One interesting point has arisen on the recent 15,000 miles test in France on the 20 HP, that is that the exhaust valves made in Firth's Crown Austenitic, steel is nothing like as good as the Silchrome material. We have since carried out tests on the bed which shew conclusively that Firth's Crown Steel scales badly if over-heated. The advantage it has is that its strength at high temperatures is much better than Silchrome. It was this feature which gave us the advantage when they were fitted to the "R" engine. Actually, on the car we had two or three exhaust valves in Firth's Crown Steel burned partly away. It occured once, and then a daily check was kept on the tappet clearance but it still occurred again. As we never had a single failure with Silchrome exhaust valves we think it advisable to carry on with that material. As regards the new gear-boxes. We have tried with E.{Mr Elliott - Chief Engineer} and Da.{Bernard Day - Chassis Design}, an Armstrong Siddeley car. One has to admit that the operation of the gears on the Armstrong Siddeley is ideal. The difficulty of changing the gear simply does not exist. We found, however, on the particular sample we tried, a considerable difficulty in getting a smooth pick up from a standing start either forward or reverse. One does not see why this should be innerent in the design and possibly we were just unfortunate. A personal friend of mine is agent for these cars in Derby and his view is that they have not been taken up enthusiastically by the public, but the four or five cars | ||